Run out of memory

#1

Hi, I've been looking into ObjectDB for our use, where everything has been great apart from I'm stuck on the following problem.

I am trying to load a large file (> 1GB), process certain information and store it back in the database to access / modify later. I require to be able to rollback changes as well, where there can be massive amount of changes.

I have been storing the data using a single entity manager and following the batch shown at http://www.objectdb.com/java/jpa/persistence/store#Batch_Store_. However the problem is that it seems that even calling flush followed by clear the uncommitted changes persist in RAM (not the file db), hence I am getting out of memory exceptions.

Here are snapshots of my code:

protected void onBegin() {
    this.em = this.emf.createEntityManager();
    this.em.getTransaction().begin();
}

protected void insertDatabaseData(DatabaseData data) {
    this.em.persist(data);
    if (this.commitCount.getAndIncrement() >= 5000) {
        this.commitCount.set(0);
        this.em.flush();
        this.em.clear();
        System.err.println("Flushing");
    }
}

protected void onCommit() {
    this.em.getTransaction().commit();
    this.em.clear();
    this.em.close();

    System.err.println("Commit Done");
}

protected void onRollback() {
    this.em.getTransaction().rollback();
    this.em.clear();
    this.em.close();
    System.err.println("Rollback Done");
}

The general call of these functions are:

onBegin();

for (DatabaseData d : lotsOfData)
    insertDatabaseData(d);

if (commit)
    onCommit();
else
    onRollback();

If anyone can see what is going wrong I would really like to know. I am running the current version 2.2.7_04.

Cheers,

Dave

#2

Calling flush followed by clear frees memory at the EntityManager (client side in C/S mode), but the ObjectDB storage engine (server side in C/S mode) still keeps the changes in memory until commit.

As a result, the transaction size is limited by the available JVM heap size. Actually to be able to store 1GB of data in a single transaction you currently need about 2.2GB of available JVM heap.

Therefore, at least in the current ObjectDB version - very large transactions should be avoided.

If very large transactions are essential for your project, please create a support ticket to discuss possible solutions.

 

ObjectDB Support
ObjectDB - Fast Object Database for Java (JPA/JDO)

Post Reply

To post a reply and/or subscribe to update notifications - please login